1. Field of the Invention:
The present invention relates to a piston for internal combustion engines and the like and more particularly to a piston which incorporates operative portions which automatically adjust to deviation in piston movement within its cylinder substantially to eliminate scoring and other damage to the cylinder wall caused by such deviant movement of the piston within the cylinder and which facilitates the replacement of worn or damaged piston rings borne by the piston.
2. Description of the Prior Art:
It has long been known that the efficient operation of devices, such as internal combustion engines and pumps of various types, requires that the piston of the subject device seal effectively against the walls of its associated cylinder to permit effective compression to take place in the device. Sealing of the piston against the associated cylinder wall is accomplished through the use of piston rings that are deployed at various positions along the piston body. Conventional pistons used in internal combustion engines employ piston rings which are deployed in fixed relation about the piston body in recesses formed in the piston body. While this method of sealing the piston against the associated cylinder wall has long been employed, it has significant shortcomings.
For example, engineers and engine mechanics have long known that the damage to cylinder walls is caused, in part, by deterioration over time of the piston rings borne by the piston. Manifestations of piston ring deterioration, of course, include decreased engine efficiency and loss of power. These manifestations are a direct result of a loss of adequate compression due to inadequate sealing of the piston against the cylinder wall.
While some scoring or other damage to the internal surface of the cylinder wall can occur prior thereto as will hereinafter be discussed, as the piston rings deteriorate the damage to the cylinder wall increases at a progressive rate. The mechanism of this damage has been determined to lie in the fact that when the piston rings become sufficiently worn due to the action of friction upon them, the piston rings permit the piston to deviate somewhat from its axial path of reciprocal movement in the cylinder. As the piston deviates from its axial path of movement, the rings, which are captured in a conventional configuration, are deformed somewhat and the edges thereof are diverted from their facing engagement with the cylinder wall. Contact of the edge of the piston ring with the cylinder wall causes scoring of the cylinder wall. If such a condition is allowed to go unremedied for a substantial period of time, significant damage to the cylinder results. The repair of such damage to the cylinder often requires that the cylinder be rebored or a sleeve inserted to provide a new internal surface.
Furthermore, the replacement of worn piston rings, whether before or after damage to the cylinder wall, is a rather complex and laborious process with conventional pistons. It requires removal of the piston from the engine by disconnecting the piston rod, replacement of the worn piston rings and subsequent remounting of the piston, bearing the new piston rings, in the engine. The remounting operation alone is difficult in that it must be accomplished with great care in order to avoid damage to the cylinder wall.
Damage to the piston rings and to the cylinder wall is not due in total part to deterioration of the piston rings themselves. Those skilled in the art have long known that when a piston travels in a cylinder through top and bottom center, there is created, what is known in the art as "lateral thrust pressure". Lateral thrust pressure, in a conventionally designed piston, acts on the piston to cause it to deviate in slight lateral movement from its intended axial path. It has been determined that the lateral thrust pressure is exerted most strongly in the area of the piston occupied by the piston ring that is nearest the combustion surface end of the piston body. Such lateral thrust pressure which causes the deviant movement of the piston body is the force which moves the piston rings from facing engagement with the cylinder wall, thus permitting the piston rings to score the walls of the cylinder. Deterioration of the cylinder walls is also caused, in some respects, by the fact that the area of the cylinder wall adjacent to the piston rings nearest the combustion surface end of the piston body is an area of the cylinder wall which is generally not as well lubricated as other areas. Furthermore, lateral thrust pressure may cause damaging contact by other portions of the piston body with the cylinder wall.
Therefore, it has long been known that it would be desirable to have a piston which would operate in such a manner as to prevent the scoring and other damage to its associated cylinder wall which has heretofore been the result of worn piston rings and lateral thrust pressure, and furthermore to have a piston which could be serviced and maintained without requiring the removal of the piston and rod assembly from the engine.